1. Field of the Invention
The present invention relates to an optical subassembly that provides an optical receptacle adhered to an optical device with a transparent resin package.
2. Related Prior Art
The YAG laser welding has been well known in the filed to assemble an optical receptacle with an optical device precisely and firmly. The YAG laser may heat members to be welded so as to melt them locally. Accordingly, the members to be welded are required to have a lesser thermal conductivity to cause the local melting even when they are metallic material.
Recently, an optical subassembly primarily made of resin has been practical by responding to a continuous request to reduce the cost thereof, in particular, the optical subassembly for an application of the short reach has been strongly requested to lower the cost and the price. Such a subassembly often uses a resin package and an adhesive to assemble the subassembly. The optical alignment of the subassembly is required in the alignment between components with the accuracy below several micron-meters, generally smaller than 2 micron-meters for the application using a single mode fiber. Moreover, the optical subassembly with the optical receptacle reiteratively receives an optical plug in the optical receptacle, and is necessary to keep the optical coupling efficiency as withstanding the external stress caused in an insertion/extraction of the optical plug.
To widen an area to be glued and to use an adhesive showing a superior adhesive strength results in a secure adhesion. In the assembly of the optical subassembly, therefore, two types of the adhesive are generally used; one is a type of ultraviolet curable adhesive and the other is a type of thermally curable adhesive. Applying the ultraviolet curable adhesive to members to be attached, aligning the members optically, curing the adhesive by irradiating the ultraviolet rays as the alignment between members are maintained, applying the thermo-curable adhesive and solidifying it by raising an ambient temperature, the optical subassembly primarily with resin bodies is completed.
Japanese Patent Application published as JP-2008-116861A has disclosed an optical subassembly that provides a sleeve member and an optical device each having a resin body and being bonded with the ultraviolet curable resin. The sleeve member has openings or cuttings in a portion to cover the optical device so as to expose the ultraviolet curable resin. The openings or cuttings enhance the hardening of the ultraviolet curable resin. However, openings or cuttings cause a non-uniform thickness of the resin, which results in the optical misalignment between the sleeve member and the optical device during the hardening of the resin. Additionally, although an amount of the curable resin increases, an area to be bonded is not increases, the adhesive strength between the sleeve member and the optical device is not achieved.
The U.S. Pat. No. 5,596,665, has disclosed another optical subassembly, in which a sleeve member and an optical device are attached with an ultraviolet curable resin, in particular, one of the bore of the sleeve member and the periphery of the optical device provides a circumferential hollow and the bore provides a reflective surface for the ultraviolet rays to enhance the hardening of the curable resin by deeply penetrating the ultraviolet rays.